1. The Field of the Invention
The present invention relates to methods and systems for treating tooth surfaces. More particularly, the present invention is directed to methods and systems for activating dental bleaching compositions on a person""s teeth. The methods and systems for activating the bleaching compositions utilize a dental light guide configured to focus radiant energy on the person""s teeth being treated.
2. Relevant Technology
The use of certain foods and tobacco, the process of aging, diseases, trauma, medications, some congenital conditions, and environmental effects can cause teeth to become discolored. Because white or whitened teeth are usually considered to be aesthetically superior to stained or discolored teeth, there has been a heightened level of interest of late in developing compositions and methods for bleaching teeth.
A tooth is comprised of an inner dentin layer and an outer hard enamel layer that is slightly porous. The outer layer is the protective layer of the tooth. The natural color of the tooth is opaque to translucent white or slightly off-white.
Some dentifrices, like toothpastes, gels, and powders contain active oxygen or hydrogen peroxide liberating bleaching agents. Such bleaching agents include peroxides, percarbonates and perborates of the alkali and alkaline earth metals or complex compounds containing hydrogen peroxide. Also, peroxide salts of the alkali or alkaline earth metals are known to be useful in whitening teeth.
The most commonly used dental bleaching agent is carbamide peroxide (CO(NH2)2xc2x7H2O2), also called urea hydrogen peroxide, hydrogen peroxide carbamide, and perhydrol-urea. Carbamide peroxide has been used by dental clinicians for several decades as an oral antiseptic. Tooth bleaching was an observed side effect of extended contact time. Over-the-counter compositions of 10% carbamide peroxide are available as xe2x80x9cGLY-OXIDE(copyright)xe2x80x9d by Marion Laboratories and xe2x80x9cPROXIGEL(copyright)xe2x80x9d by Reed and Carnrick. An extended-contact application of bleaching gel held in a dental tray is available as xe2x80x9cOPALESCENCE(copyright)xe2x80x9d by Ultradent. Other bleaching agents such as peroxyacetic acid (CH3Cxe2x95x90OOxe2x80x94OH) and sodium perborate, are also known in the medical, dental and cosmetic arts.
People who have desired to have their teeth whitened have typically done so by applying a bleaching composition to the teeth by means of the dental tray for repeated treatments, or they had to submit to conventional in-office bleaching techniques that required from 4 to 10 visits to the dental office before clinically significant results were achieved. Less effective teeth whitening was also done by the use of toothpastes or polishes that were applied by brushing. Clinically significant results are quantifiable such as by measuring gray scale, L*, and as to yellowness or blueness, b*, in the CIE(copyright) system of color measurement or by equivalent methods.
Bleaching compositions have been manufactured in one-part and two-part systems. A one-part system consists of a compound in which the active bleachant is dispersed into inert components to form an emulsion or gel. One-part systems can also further consist of mixtures in which stabilizers are used to prevent premature decomposition of the peroxide in the bleaching composition. The advantage of a one-part system is ease of use and convenience. The main disadvantage is that prior art one-part bleaching compositions generally contain relatively low concentrations of peroxide due to the instability of more highly concentrated peroxide compositions. Thus, current one-part systems have a low potency and are slow to react. Most one-part systems in the past have included active peroxide in a range of up to about 3.5% by weight. Due to the relatively low concentration of active bleaching agent in one-part systems, about 10 applications on average are necessary for effective bleaching.
In a two-part system, aqueous hydrogen peroxide is stabilized in a first part, while activators (i.e., destabilizers) are contained in a second part. These components are mixed just prior to bleaching in order to cause decomposition (i.e., activation) of the hydrogen peroxide at the time of use. The main advantage of a two-part system is that it allows for much higher concentrations of active peroxide that cannot exist stably as a one-part system for incidental off-the-shelf use. This results in faster bleaching of the person""s teeth due to the higher peroxide concentration. Faster bleaching is desirable, especially where the person undergoing treatment finds it difficult to comply with longer bleaching regimens, or if only one or a few teeth need bleaching. A disadvantage of two-part systems is the inconvenience of having to mix the components just prior to use.
Another example of a two-part system is microencapsulation of the bleaching agent and a stabilizer. The microcapsules would separate the bleaching agent from the carrier and other materials and would rupture only upon physical shear caused by a tooth brush. Like other one-part systems, the dental bleaching effect of the microencapsulation system is only visible after prolonged use due to its low peroxide concentration or low activation rate.
Although positive results using the foregoing techniques have been reported, the effectiveness of the techniques depends upon such factors as type and intensity of the stain, bleaching agent contact time on the teeth, the amount of available active bleachant in the bleaching agent, and the persistence of the individual in applying the treatment until the desired result is accomplished.
Notwithstanding the foregoing advantages, there remain some important disadvantages to current one-part and two-part systems. A disadvantage to the two-part system is that the bleaching composition must be mixed on-site in the operatory immediately before application to the person""s tooth. Mixing requires additional time by the dental professional, which lowers efficiency and represents an extra preparatory procedure. Mixing in proper amounts is also important in order to yield consistent results.
Another disadvantage with two-part bleaching compositions is that, once mixed, the bleaching compositions must be used soon, since they are unstable and tend to decompose through the release of oxygen from the peroxide moieties. Often, the constituents of the bleaching compositions themselves accelerate decomposition rates. While such accelerants are useful in promoting faster bleaching, they yield a composition having a very short lifespan. Because known accelerants are chemical in nature, they cannot be added until bleaching is to commence. Otherwise the premature release of active oxygen will quickly decrease the potency of the bleaching composition. Moreover some accelerants or peroxide indicators reduce bleaching ability since they themselves consume the peroxide, thus competing with the teeth for the peroxide.
In view of the foregoing, it will be appreciated that what is needed in the art are methods of treating tooth surfaces with stable, one-part dental bleaching compositions that allow for greatly increased bleaching rates compared to existing one-part systems.
Additionally, it would be a significant advancement in the art to provide methods for treating tooth surfaces with stable, one-part dental bleaching compositions that included means for triggering or accelerating the release of active oxygen from the bleaching agent when needed but which did not cause premature decomposition of the active dental bleaching agent or destruction of the bleaching agent activator prior to use.
It would be a further advancement in the art to provide methods for treating tooth surfaces with stable, one-part dental bleaching compositions that include higher concentrations of bleaching agent compared to existing one-part compositions.
There is also a need in the art to provide methods for treating tooth surfaces with a dental bleaching composition that included an agent that could cause accelerated activation of the bleaching agent upon irradiating the dental bleaching composition with radiant energy.
It would be yet another advancement in the art to provide methods and systems for increasing the rate of bleaching activity of a dental bleaching composition by directing radiant energy simultaneously over the entire area of teeth to be treated without having to redirect the radiant energy source to irradiate all of the teeth being treated.
It would further be an improvement in the art to provide methods and systems for increasing the rate of bleaching activity of a dental bleaching composition if the radiant energy could be more accurately focused onto the person""s teeth to be treated rather than onto surrounding tissues, particularly sensitive oral tissues.
Such compositions, methods and systems for accelerated treatment of tooth surfaces with stable, one-part dental bleaching compositions are disclosed and claimed herein.
The present invention is directed to methods and systems for treating tooth surfaces with dental bleaching compositions, more particularly, stable one-part dental bleaching compositions having relatively high concentrations of a dental bleaching agent and a radiant-energy activating agent that acts to accelerate bleaching activity upon irradiating the dental bleaching composition with radiant energy. Hence, the bleaching rate of the bleaching composition is accelerated using an apparatus for directing radiant energy onto the tooth surfaces to be treated. The preferred apparatus is a novel dental light guide that is able to simultaneously direct radiant energy on a desired number of the teeth of a dental arch to be treated, while remaining in a substantially fixed position relative to the dental arch.
The dental bleaching compositions of the present invention include stable, one-part, pre-mixed compositions with a sufficient shelf life to allow for long-term storage and use as needed. Preferred bleaching agents include peroxides such as hydrogen peroxide and carbamide peroxide (which is a complex between urea and hydrogen peroxide). A thickening agent can be used to give the dental bleaching composition a desired consistency, stickiness, and viscosity. Preferred thickening agents include PEMULEN(copyright), a proprietary compound from B.F. Goodrich, or a compositional or chemical equivalent thereof.
An important advantage of the preferred bleaching compositions of the present invention are that they are stable over time. A major cause of premature degradation of the bleaching agent is the existence of errant or residual metal ions that can act as bleaching agent catalysts. Hence, it is possible to create stable bleaching compositions even at high concentrations (greater than 20% by weight) by avoiding, removing, or trapping errant or residual metal ions. Scavenging of errant or residual metal ions can be accomplished by means of a bleaching agent stabilizer. The bleaching agent stabilizer comprises edetate disodium, EDTA, oxine EDTA, calcium disodium EDTA, adipic acid, succinic acid, citric acid, tin nitrates, tin phosphates, their respective salts, their combinations, and the like.
Activation of the dental bleaching composition of the present invention is accomplished with a bleaching agent activator that is preferably a radiant-energy or heat-energy absorbing substance. Examples of such substances include radiant-energy absorbing, substantially conjugated hydrocarbons such as aromatic hydrocarbons, multiple double-bond hydrocarbon chains, chain-aromatic mixtures, reacted combinations thereof, and equivalents. Specific examples include caroteneoids such as bixin, lycoxanthin, lycophil, canthaxanthin, capsanthin, cryptoxanthin, isomers of carotene, and lycopene. Other specific examples include aromatics such as coronene, fluoranthene, naphtho[2,3-a] pyrene, trans-4,4xe2x80x2-diphenylstilbene, 9,10-diphenylanthracene, 5,12-bis (phenyethynyl) napthacene, 9,10-bis (phenylethynyl) anthracene, and perylene. The foregoing compounds may optionally include one or more carboxyl groups. The only limitations are (1) that the radiarit-energy absorbing substance does not cause substantial peroxide decomposition over time, and (2) that the radiant-energy absorbing substance be relatively stable in the presence of the bleaching agent over time. Preferred bleaching agent activators include 9,10-bis (phenylethynyl) anthracene, perylene, and isomers of carotene and carboxyl-substituted variations thereof.
The inventive bleaching compositions preferably include an inert carrier, including but not limited to, water, polypropylene glycol, polyethylene glycol, sorbitol, propylene glycol, glycerol, steryl alcohol, large molecular weight polyols, mixtures of the foregoing, and equivalents.
Because the bleaching compositions of the present invention are both stable in a one-part, pre-mixed system and include the radiant-energy absorbing substance, the bleaching process is greatly simplified. The dental bleaching compositions may advantageously be either preloaded or loaded manually into and dispensed from a syringe onto the person""s teeth. The dental professional simply expresses a desired quantity of the dental bleaching composition over the person""s teeth to be treated and then triggers accelerated bleaching by either irradiating the bleaching composition with radiant energy, such as visible and/or UV light, or by applying, e.g., conductive heat energy to the composition before, during, or after application to the teeth. Depending on the desired rate of bleaching and sensitivity of the person undergoing treatment to bleaching agents, a bleaching composition having the optimum amount of bleaching agent can be selected before bleaching commences or can be determined by noting the results of the first bleaching treatment.
A preferred method of irradiating the bleaching composition involves using a dental light guide having an arcuate member that is configured such that a portion or all of a person""s dental arch, including the treated teeth, may be positioned in close proximity to an inner surface thereof. The inner surface of the arcuate member has one or more light-emitting panels thereon in a location such that the labial surfaces of the treated teeth may be irradiated. The light guide further includes a light source and a plurality of optical fibers or other light-transmitting means to carry radiant energy to the light-emitting panels. The light guide can be configured to cover part or all of the upper dental arch, part or all of the lower dental arch, or part or all of both the upper and lower dental arches.
According to a preferred method of the invention, after the dental bleaching composition has been applied to the selected teeth, the light guide is introduced into the person""s mouth such that the selected teeth are in close proximity to the arcuate member. The radiant energy source of the light guide is activated to cause radiant energy to pass through the light-emitting panels onto the treated teeth. The bleaching rate of the bleaching composition accelerates in response to the introduction of radiant energy in close proximity to the teeth being treated. The light guide is kept in place over the treated teeth until a desired amount of bleaching has occurred.
By use of the foregoing light guide, a practitioner may irradiate tooth surfaces without needing to redirect the light guide onto different teeth. Instead, the preferred light guide remains in a fixed position in relation to the dental arch. As a result, the practitioner may easily monitor the overall amount of time that the treated teeth are irradiated. Moreover, the amount of time that individual teeth are treated can easily be determined, thereby facilitating uniform bleaching. Simultaneously irradiating the complete set of treated teeth within a single dental arch decreases the length of the treatment session that would otherwise be required.
In view of the foregoing, it is an object of the present invention to provide methods for treating tooth surfaces with stable, one-part dental bleaching compositions that allow for greatly increased bleaching rates compared to existing one-part systems.
It is a further object and feature of the present invention to provide methods for treating tooth surfaces with stable, one-part, pre-mixed viscous/gelled dental bleaching compositions that include means for triggering or accelerating the release of active oxygen from the bleaching agent when needed but which does not cause premature decomposition of the active dental bleaching agent or destruction of the bleaching agent activator prior to use.
It is still a further object and feature of the present invention to provide methods for treating tooth surfaces with stable, one-part dental bleaching compositions that include higher concentrations of bleaching agent compared to existing one-part compositions.
It is a further object and feature of the present invention to provide methods for treating tooth surfaces with a dental bleaching composition that includes an agent that causes accelerated activation of the bleaching agent upon irradiating the dental bleaching composition with radiant energy.
It is yet another object and feature of the present invention to provide methods and systems for increasing the rate of bleaching activity of a dental bleaching composition by directing radiant energy simultaneously over the entire area of teeth to be treated without having to redirect the radiant energy source to irradiate all of the teeth being treated.
It is a further object to provide methods and systems for increasing the rate of bleaching activity of a dental bleaching composition where the radiant energy can be more accurately focused onto the person""s teeth to be treated rather than onto surrounding tissues, particularly sensitive oral tissues.
These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.